What open source architecture design tool do you recommend?

First, my software IDE is eclipse IDE. I have separate installs for C, Java, snd others

Second, for simple diagrams, I use DIA

Third, for my schematics, I rely on KiCAD.

Fourth, I have been trying to get my head around Papyrus using sysML (from the folks at eclipse) for system flows.

Fifth, for programming I really like C (GCC) (not C++) and Java (community)

Sixth,  I use LibreOffice Writer for much of my documentation, but It gets published in Correl Ventura ( I have more control).

AND Lastly, anything from MS is suspect and just trash and NOT OPEN SOURCE!!!

lol I wish MS would fix this:

https://office-watch.com/2022/make-lines-arrows-straight-word-bug-fix/ 

My (not so) secret technique for almost every diagram, work related or otherwise, is to use/misuse PowerPoint, and a benefit is that anyone can modify my diagrams since managers often want to strip off some complexity and reuse the diagrams for their high-level purposes too, and they already have Office on their PCs so they don't need to load anything special. Libre Office equivalent is presumably just as useful. 

Another excellent tool/time-saver is Snagit (I dont know what the closest Linux equivalent would be for that), which is extremely feature rich and allows me to convert almost any image into transparent PNGs for dropping into PowerPoint, to use in diagrams. There are so many uses for Snagit, and it's gone up in price unfortunately, but it's still cheap for what it does, considering I get use out of that app every day.

easy fix don't use their stuff!!! LOL, I you use it then you shouldn't mone (sp??) over their stuff. The best solution is to just get over  it and switch to LINUX and open source software!! and KiCAD did not cost me a dime!!

Install Linux on Windows with WSL: https://docs.microsoft.com/en-us/windows/wsl/install and get the best of both!!! lol

Is there a big difference between word and powerpoint for diagrams? Is it that in powerpoint everything defaults to anchoring to position versus text?

Neat tool, snagit, I will take a look. The snipit to in windows has been a game changer for me. WinKey+Shift+S.  But, if I want to annotate it, then I have to paste it into another program like paint. The annotation tools in the win snippit are lousy.

Is there a big difference between word and powerpoint for diagrams? Is it that in powerpoint everything defaults to anchoring to position versus text?

Neat tool, snagit, I will take a look. The snipit to in windows has been a game changer for me. WinKey+Shift+S.  But, if I want to annotate it, then I have to paste it into another program like paint. The annotation tools in the win snippit are lousy.

Hi!

Word is missing a few drawing features, for instance, it's not possible to union/subtract shapes (as far as I'm aware). Also I'm not sure about the export capabilities. With PowerPoint, with a registry edit, it can do very high DPI for diagrams to place into a blog.

The Windows snipping tool is good, although it has a subset of Snagit features. Snagit has a mix of these features: screenshotting and reviewing (timestamped and stored forever), screen/sound/mic recording, animated GIFs, annotation, image editing, creating transparent PNGs. Pretty much all of these features are executed well. I sometimes annotate directly within Snagit, or alternatively clean up an image (e.g. make the outside transparent) and bring it into PowerPoint and annotate there.